Such a reactor is generally known in the state of the arts There, a wafer is held at a very small distance from facing walls of the reactor by gas flowing from both sides of the wafer. This gas comprises the required reactants. Such a reaction can take place at a comparatively high temperature such as approximately 1000.degree. C. To that end, the walls or plates of the floating wafer reactor are heated, which takes place with the help of heating elements. The energy supply to these electrical heating elements takes place by means of a controller which is regulated by sensors which are either close to the processing area or somewhat deeper in the walls of the floating wafer reactor. The gas supplied to the processing area is heated to the desired temperature beforehand. Apart from the entering and leaving of wafers, the temperature control is comparatively easy and, temperature-wise, a very stable system arises, as the furnace should preferably be continually at the same temperature.
Problems occur during the entering of the wafers in the processing area, however. These will generally be at a comparatively low temperature, for example, at room temperature. Due to the small distance between the walls of the reactor and the wafer, a very rapid heating of the wafer takes place, typically from some seconds to some minutes. The heat capacity of the wafer is much smaller than the heat capacity of the walls. In a typical case, when the temperature of the wafer is elevated from room temperature to 1000.degree. C., a lowering of the temperature by approximately 10.degree. C. occurs immediately on the border between the walls and the processing area of the reactor. Internally of the walls, that is, further away from the border with the processing area, this temperature decrease will be smaller and, if no fiber measures are taken, a temperature drop of the walls of approximately 3.degree. C. can be caused in the long term. This is obviously compensated for by the detection of the sensors present in the walls which will supply extra energy via the controller to the heating elements.
As the heating elements are some distance from the processing area, and the area in between will generally be filled with a ceramic material with a certain heat capacity where the heat is not optimally conducted, there will be some time lag.
For a number of processes, this is particularly undesirable. There, it is important that the temperature in the processing chamber is kept within a narrow range and may not be too high or too low, to be able to correctly control the reaction which takes place in the processing chamber.